Avoid processing popular posts twice

Problem: Messages are being fetched with `post.get()`, which runs the
`transform()` function to decorate them with Markdown/etc, but then
they're being passed through `transform()` a second time at the end of
the function. This is inefficient and applies side-effects (like adding
channels to the post) twice.

Solution: Remove the final `transform()` so that these posts are only
decorated once.

Fixes: https://github.com/fraction/oasis/issues/358

src/models.js

@@ -1065,7 +1065,7 @@ module.exports = ({ cooler, isPublic }) => {
                   if (err) {
                     reject(err);
                   } else {
-                    resolve(transform(ssb, collectedMessages, myFeedId));
+                    resolve(collectedMessages);
                   }
                 })
               );